Variational Quantum ML | Turn lessons into working experiments

Starter code

module rzz_vqe_ansatz;
use chemistry.h2_minimal;

fn main() {
  let q: QReg<2> = qreg[2];
  param theta: Angle[4] = [0.2, 0.1, 0.4, -0.2];

  X(q[0]);
  Ry(q[0], theta[0]);
  Ry(q[1], theta[1]);
  RZZ(q[0], q[1], theta[2]);
  Ry(q[0], theta[3]);

  let energy = expect H2Minimal;

  return energy;
}

Expected output

Angle[N] expands into theta_0, theta_1, theta_2, and theta_3

RZZ creates the interaction layer between q[0] and q[1]

Output reports the H2Minimal energy expectation

Resources include the two-qubit interaction gate used by the ansatz

Debugging checklist

Run the circuit and read the energy expectation in Output

Open the Circuit tab and find the RZZ interaction

Change theta[2] and compare the energy

Replace use chemistry.h2_minimal with an inline observable block

Explain which theta entry controls each ansatz layer

Extension challenge

Add another RZZ/Ry layer with theta[4] and theta[5], then compare the resource estimate and energy.